Virus informatique | EPFL Graph Search

thumb|alt=Du code hexadécimal en jaune sur fond bleu|Code sur un ordinateur infecté par le virus Stoned. Un virus informatique est un automate logiciel autoréplicatif. Certains sont inoffensifs, d'autres contiennent du code malveillant (ce qui entraine le classement du logiciel comme logiciel malveillant). Dans tous les cas, un virus informatique est conçu pour se propager sur d'autres ordinateurs en s'insérant dans des logiciels légitimes, appelés « hôtes » à la manière d'un virus biologique. Il peut perturber plus ou moins gravement le fonctionnement de l'ordinateur infecté. Un virus se répand par tout moyen d'échange de données numériques, comme les réseaux informatiques ou les périphériques de stockage externes (clés USB, disques durs, etc.). Terminologie Son appellation provient d'une analogie avec le virus biologique puisqu'il présente des similitudes dans sa manière de se propager en utilisant les facultés de reproduction de la cellule hôte. On attribue le terme de

Viral Transfer and Inactivation through Zooplankton Trophic Interactions

Virginie Bachmann, Xavier Fernandez Cassi, Niveen Saad Ismail, Tamar Kohn, Margot Ninon Lauren Olive

Waterborne viruses are responsible for numerous diseases and are abundant in aquatic systems. Understanding the fate of viruses in natural systems has important implications for human health. This research quantifies the uptake of bacteriophage T4 and the enteric virus echovirus 11 when exposed to the filter feeders Tetrahymena pyriformis and Daphnia magna, and also examines the potential of viral transfer due to trophic interactions. Experiments co-incubating each species with the viruses over 72-96 hours showed up to 4-log virus removal for T. pyriformis, while direct viral uptake by D. magna was not observed. However, viral uptake by D. magna occurred indirectly by viral transfer from prey to predator, through D. magna feeding on virus loaded T. pyriformis. This predator-prey interaction resulted in 1-log additional virus removal compared to removal by T.pyriformis alone. Incomplete viral inactivation by D. magna was observed through recovery of infective viruses from daphnid tissue. This research furthers our understanding of the impacts of zooplankton filter feeding on viral inactivation and shows the potential for viral transfer through the food chain. The viral-zooplankton interactions observed in these studies indicate that zooplankton may improve water quality through viral uptake or may serve as vectors for infection by accumulating viruses.

2020

Experimental adaptation of human echovirus 11 to ultraviolet radiation leads to tolerance to disinfection and resistance to ribavirin

Virginie Bachmann, Anna Carratala Ripolles, Jeffrey David Jensen, Tamar Kohn, Hyunjin Shim, Qingxia Zhong

Ultraviolet light in the UVC range is a commonly used disinfectant to control viruses in clinical settings and water treatment. Here, we employed an experimental evolution approach to investigate the adaptation of human echovirus 11 to disinfection by UVC, and characterized the underlying phenotypic and genotypic changes. Repeated exposure to UVC lead to a reduction in the UVC inactivation rate of approximately 15%. Time-series next generation sequencing data revealed that this adaptation to UVC was accompanied by a decrease in the echovirus 11 mutation rate. The inactivation efficiency of UVC was additionally compromised by a shift from first-order to biphasic inactivation kinetics, a form of “viral persistence”. Importantly, populations with biphasic inactivation kinetics also exhibited resistance to ribavirin, a mutagenic drug. Overall, our results indicate that while the ability of echovirus 11 to adapt to UVC is limited, resistance may have relevant consequences to disinfection in both clinical and water treatment contexts.

2017

Multi-resistance of human enterovirus to UV-C disinfection and mutagenic nucleoside analogs

Virginie Bachmann, Anna Carratala Ripolles, Tamar Kohn, Qingxia Zhong

Disinfection is an important strategy to control the environmental transmission of human viruses. Specifically, UV254 is increasingly used to disinfect from clinical items or surfaces to drinking water. RNA virus populations have high mutation rates and large population numbers that allow them to rapidly adapt to stressors. It is therefore likely that variants with enhanced resistance to disinfection may eventually emerge in a virus population. The genetic basis and mechanisms that underpin the emergence of virus resistance to disinfection remain, however, unknown. The goal of this study was to investigate the emergence of echoviruses resistant to UV254 disinfection in vitro, and to characterize the genotypic and phenotypic changes in the resistant populations as compared to the wild-type. Resistant virus populations emerged in mutation-accumulation laboratory experiments. Each experiment consisted in exposing echovirus suspensions to a UV254 fluence such that a 4.5 log10 reduction in infective viruses was achieved, and then regrowing the survivors by infecting BGM cells at a very low multiplicity of infection (MOI>0.001). Unexposed control experiments were conducted in parallel by diluting the virus suspensions instead of exposing them to UV254 prior to regrowth. We demonstrated that echovirus populations became increasingly resistant to UV254. Interestingly, a similar extent of resistance was observed in the unexposed control experiments. Fixed mutations were repeatedly identified by next generation sequencing in the 2C and 3D protein region, both involved in the genome replication. The wild-type and resistant echovirus populations exhibited an equivalent replicative fitness under standard culturing conditions. However, the UV254-resistant mutants were more resistant to ribavirin and guanidine hydrochloride. Finally, the exposed populations were able to maintain the production of infective progeny despite the effect of such chemical mutagens. Combined, these findings suggest that multi-resistance of echovirus to UV254 disinfection and treatment with mutagenic nucleotide analogs may arise in virus populations that, subjected to repeated dramatic bottlenecks, evolve towards an increased replication fidelity. The outcomes of this work show that enteric human pathogens may exhibit multi-resistance to disinfection and clinical antiviral therapies. Ultimately, the results from this work may impact future strategies to ensure adequate control of virus environmental transmission.

2016

Multi-resistance of human enterovirus to UV-C disinfection and mutagenic nucleoside analogs

Virginie Bachmann, Anna Carratala Ripolles, Tamar Kohn, Qingxia Zhong

2016